1. Technical Field
The present invention relates to an electronic timepiece that adjusts the time based on signals from positioning information satellites such as GPS satellites, and to a control method of an electronic timepiece.
2. Related Art
Electronic timepieces that receive signals transmitted from positioning information satellites such as GPS (Global Positioning System) satellites, and execute the reception process when the power supply voltage exceeds a specific voltage are known from the literature. See for example, JP-A-2009-168620.
When running the positioning process to receive satellite signals from multiple positioning information satellites, this electronic timepiece first determines if the supply voltage exceeds a specific voltage, and then determines if a reception process that takes one to three minutes can be executed. If the supply voltage exceeds the specific voltage, the electronic timepiece receives satellite signals from multiple positioning information satellites, and executes a positioning process that calculates time information and positioning information based on the received satellite signals. If the supply voltage is less than or equal to the specific voltage, the electronic timepiece ends the reception process.
Because this specific voltage is a previously set value, problems can happen when the reception process is controlled by comparing the specific voltage and the supply voltage.
For example, when a battery is used as the power supply and the temperature drops, the internal resistance of the power supply rises and the voltage drop that results from running the reception process to receive satellite signals increases. The specific voltage must therefore be set appropriately to the lowest limit (such as −10° C.) of the temperature range in which the electronic timepiece is expected to be used. This enables preventing the control chip from shutting down due to a drop in the supply voltage during the reception process when the positioning reception process executes in a low temperature environment near the lowest limit of the temperature range.
However, even though the specific voltage can be set to a lower voltage at temperatures above this low temperature range because the voltage drop from the reception process is lower than in the low temperature range, the specific voltage is still set to a level at which a system shutdown can be prevented even in the low temperature range. As a result, the reception process cannot be executed if the supply voltage is lower than the specific voltage even if the supply voltage is at a level at which the reception process could actually be executed at the current temperature.
Opportunities to acquire time information and adjust the internal time are therefore fewer, and the correct time may not be displayed.